Strip printer

ABSTRACT

A strip printer wherein an electrosensitive strip is reeled past plural, vertically aligned electrodes by means of a capstan-pinch roller combination, the capstan being driven by a constant speed motor on a continuous basis. A solenoid is coupled to the pinch roller for selective actuation causing the pinch roller to engage the strip for gripping the strip by the pinch roller and the capstan. A read only memory has character input, column addressing input and data output lines for providing sequentially data groups in the data output lines in response to signals at the character input and in further response to sequential column addressing input signals, provided by an addressing counter. The data lines are connected to the electrodes for control of electric energization thereof in response to output signals on the data lines. A constant frequency oscillator provides oscillations to the counter at a particular phase in relation to an enabling input signal, derived from a print command input, and sustained for the duration of solenoid energization so that a particular plurality of data columns in the memory are addressed in sequence and at a constant rate, for causing energization signals to be applied to the electrodes at said rate.

United States Patent Glaser et al.

[54] STRIP PRINTER [72] Inventors: Peter S. Glaser, Culver City; Jack.

'Goldberg, Northridge, both of Calif.

[73] Assignee: Electronic Arrays, Inc., Mountain View, Calif.

22 Filed: May 12,1971

21 Appl.No.: 142,572

[52] U.S. C1. .....l78/30, 346/74 SB [58] Field of Search..l78l23 R, 23 A, 30; 346/74 ES, 346/74 S, 74 SB, 74 SC Primary Examiner-Thomas W. Brown Attorney-Smyth, Roston & Pavitt 1 51 Dec. 26, 1972 5 7] ABSTRACT A strip printer wherein an electrosensitive strip is reeled past plural, vertically aligned electrodes by means of a capstan-pinch roller combination, the capstan being driven by a constant speed motor on a continuous basis. A solenoid is coupled to the pinch roller for selective actuation causing the pinch roller to engage the strip for gripping the strip by the pinch roller and the capstan. A read only memory has character input, column addressing input and data output lines for providing sequentially data groups in the data output lines in response to signals at the character input and in further response to sequential column addressing input signals, provided by an addressing counter. The data lines are connected to the electrodes for control of electric energization thereof in response to output signals on the data lines. A constant frequency oscillator provides oscillations to the counter at a particular phase in relation to an enabling input signal, derived from a print command input, and sustained for the duration of solenoid energization so that a particular plurality of data columns in the memory are addressed in sequence and at a constant rate, for causing energization signals to be applied to the electrodes at said rate.

11 Claims, 4 Drawing Figures PATENTED nae 2 s 1912 STRIP PRINTER The present inventionrelates to a strip printer of the type wherein dot columns are burnt-into electrosensitive strip by Operation of individually energizable electrodes. A fixed number of such columns is used to generate a dot pattern in representation of alpha-numericalcharacters, symbols etc.

The dot columns out of which. each character is created in such a printer, must be regularly spaced as otherwise the character could have a distorted appearance. On the other hand, the strip printer must permit printing of each individual character independently in time from printing thepreceding and the next characters, e.g., the presentation of characters for printing-may be irregular so that the strip cannot be advanced continuously (except in the special case that characters are presented at a regular rate equal to the maximum permissible rate of character presentation).

In accordance with the invention, the problem is solved by providing a strip reeling capstan which is rotating, i.e., driven by a constant speed motor, preferably a synchronous motor. A solenoid operated pinch'roller selectively presses the strip against the capstan for causing the strip to be advanced only upon solenoid energization. The dot-burning electrodes are controlled by and in response to the read out content of a read only memory, holding manifestation of the several characters and symbols. A sub-array of storage locations in the memory holding data bits for one character is collectively addressed through a character code, and the data of an addressed sub-array are presented in sequential columns to the electrodes in response to column addressing signals. It is now an important feature that these column addressing signals are derived from a counter which is incremented in response to a constant frequency oscillator operated in phase synchronism with energization of the solenoid. Accordingly, the several data columns in the addressed sub-array are presented at a constantrate within the period ofsolenoid energization, during which the strip is advanced by the capstan as rotating at constant speed, so that the data columns are printed as dot columns at accurately constant spacing in open loop operation.

The oscillator is particularly operated, so that the first data column is presented as the tape has been accelerated up to rated speed. The tape stops at a steep decelleration rate upon de'energization of the solenoid, which is carried out in response to counter advance, so that. also the spacing in between characters remains constant, irregular character placement on the strip is avoided accordingly. Ground voltage potential is applied to both sides of the strip, e.g., by a grounded rear platen and by knurled configuration of the grounded capstan, the knurling pinching minute holes through the front paper layer of the tape.

FIG. 1 is a top and front elevation of a strip printer constructed in accordance with the preferred embodiment of the invention;

FIG. 2 is a circuit diagram for controlling energization of dot burning electrodes in the printer of FIG. 1;

FIG. 3 gives representation of strip with dot pattern as printed; and

FIG. 4 is a schematic representation of a sub-array in circuitry which will be described later in the specification, with reference to FIG. 2. Particularly electrosensitive strip, such as metallized paper tape 13, is paid from a roll 11 on a turn-table 12. The turntable is journalled for free rotation in idler fashion. The tape 13 on roll 11 has an aluminum base covered with a white paper like layer, usually an insulative layer, and provided primarily for purposes of establishing contrast. The other side of the tape is provided with carbon black. In some tapes, the layers are reversed in that carbon black is directly underneath the paper layer, and aluminum provides backing for the 'tape. The strip printer provides contrasting dots on the paper by locally burning off the white cover through penetrating sparks, so that the carbon underneath becomes exposed from the front as visible, contrasting dot.

Tape 13 is reeled through a suitable arrangement of reels and idler rollers 14 to pass along a platen 15. The platen I5 is the'first electrically conductive component tape 13 encounters when reeled off roll 11. The platen 15, therefore, is particularly provided for purposes of establishing rear contact with a paper tape having aluminum as backing. The tape paper passes a contact arrangement 20 established by seven vertically stacked,

horizontally extending electrodes constructed as thin contact fingers which engage the tape. These fingers are insulated from each other and are individually energized to burn off the white paper cover in response to a relative high voltage pulse of short duration and applied to such a contact finger. Through selective control and timing of applying the voltage pulses variable, contoured dot patterns such as the contours of alphanumerical characters can be printed. In particular, each character is composed of vertical columns of dots, and the rate of contact finger energization determines the printing of sequential columns. For a constant tape advance, the column spacing will be constant accordingly.

The tape 13 passes a capstan 16 which is being driven continuously at a constant speed. by a synchronous motor 17 inside of housing 10. It is an important feature of this invention that the capstan is not motion-controlled but provides very accurately constant speed by being driven by the synchronous motor 17. The printer is provided with a cover (not shown) which covers all these various components except that it leaves a window in front of platen l5 and to the left of capstan 16 to permit withdrawal of printed tape as leaving engagement with the capstan to the left thereof.

spring-biased; The pinch roller periphery projects somewhat from the cradle to engage tape 13 from the rear",'the pinch roller being radially aligned with capstan 16.:A solenoid 22 with a projecting plunger 23 is disposed behind the cradle. Upon energization of the solenoid, plunger 23 pivots the cradle 19in clockwise direction, when seen from the top, to thereby urge pinch roller '18 towards capstan 16. As a consequence,

the tape in between is firmly gripped between rollers 16 A and 18 and advanced.

Due to the-vertical-capstan arrangement, retraction Proceeding now to the description of FIG. 2, there is illustrated schematically the grounded platen but additional grounding may occur by operation of the capstan l6. lnaddition, the paper strip 13 is indicated,

schematically in front of the contact fingers 20. There are alltogether seven such contact fingers for dot writing; however, the contact assembly'includes another finger individually denoted by reference number 24, which operates as asensing feeler in thatit is normally separated from the grounded platen by the tape, particularly by the paper insulation thereof; if the paper should run ou't,'contact finger 24 isgrounded and pro- I vides an inhibiting signal to the circuit to be described force forthe cradle is not providedv nor necessary as a gagement with the tape from therear. Within a few millis econ'ds, the tape is up to rated speed, equal to the constant rotational speed of capstan 19. Therefore, during'printing, the tape is extremely accurately transported at constant speed. As the solenoid de-energizes,

the relaxation of. plunger pressure, of course, amounts to an instant stopping, within a millisecond or thereabouts, of thetape. It was found that in reality the tapeiadv'ances, in absolute terms, very little during the necessary periods of acceleration or deceleration; this residual. motion is practically not visible. In other words, there is very little asynchronous progression of the tape. Moreover,'the acceleration and deceleration phases themselves are quite constant so that upon stop and go operation, i.e., uponsteppingmotion for each character printing step, the character spacing remains very accurately constant indeed, which is important for legibility of the print-out. During character writing, the tape speed is constant, so that the columns of dots composing a character, are accurately spaced for distortion free printing, provided these columns are presented for printing at a constant rate.

The capstan 16 is preferably made of metal, such as brass, with a' knurled contour, which aids in the gripping action. Moreover, the knurling is to be developed am rather fine pattern. As a consequence, it-

was found tlratfthe knurled capstan, when having paper urged against its periphery by operationof the solenoid operated plunger, penetrates the front insulation layer a of thetape. Electric contact is made between the aluminum layer underneath and the capstan so that the 7 aluminum layer of the tape becomes grounded. This completes the" circuit for dot writing throughout burning by operation of the contact 20. Thus, the tape is grounded either through the platen fromv the rear or through the capstan acting on the front or through both elements.

I to pivot cradlel9, and pinch roller 18 enters into ennext.

- The strip printer is'presumed to interface with apparatus that provides the following signals. First of all, the printer will receive a print-command signal in an input line 31.This can be regarded as a print request signal provided by the interfacing unit that also provides a charactercode to be printedFor example, a six bit character code-may be provided externally and applied to six input terminals 30. That code may, for example,'be an ASCl l code, i.e., it is a suitable and conventional code for identifying alpha-numerical characters. These characters, represented in code,- are the characters to be printed and willnormally include the letters of the alphabet, theten digits 0 through 9, and other convenient symbols such as brackets, mathematical symbols, percentagesymbols, signs, etc.; also conventional punctuation marks are included in that code. Altogether, 64 different characters can be identified by this six-bit code. I

The principal print control portion of this circuit is a READ ONLY memory 32 which is an' integrated circuit chip of the MOS'variety. It has anumber of input terminals and six of them are provided to receive the character code in that-lines 30 connect to the six input terminals that interface with the external, character codejsu'pply unit.'The READ ONLY memory may be constructed, for example, to have a large array of fixed data storage locations, and each character code addresses'a sub-array of storage cells.

A sub-array in the ROM matrix may be defined by seven rows, and, for example, six columns. The rows define read-out lines and merge in seven data output lines within the ROM chip, to which connect seven read-out busses33 (-33-1 33-7) of the chip. The sub-array is addressed as a whole by a character code as stated, but the six columns of the sub-array are internally addressed sequentially and in response to internally decoded binary addressing signals. applied 'to three additional input terminals 34 for the ROM chip. The ROM chip interpretes these binary signals as column addresssignals-within the sub-arrays selected by the character code, and data bits are sequentially provided in the output lines 33, on data column with seven bits each at a time, and in thesequence of the column addressing signals as received in input lines 34.

Finally, ,the' ROM chip receives high frequency (about Kc) clock pulses of alternating phases, O and 0 from an oscillator 37 which may be local to the strip printer, or clock pulses .may be furnished by the same source that provides the print command signal. An external output inhibit signal in a line 38 clamps the output lines 33 to zero or ground level. during each address change.

The character generation results in the production of five data columns proper per character preceded and Succeeded by seven data bits whereby, for example, a bit of value 1 represents an energize command for adot printing (burning) electrode and a binary zero represents a non-energization state.

FIG. 4 illustrates schematically a sub-array of altogether 42 storage locations to the bit level and holding representation for dot printing'the character A. The first column is an all zero column; the second through sixth columns holdthe character defining bits. An all zero,-seventh column is simulated through addressing of a seventh, not implemented column, whereupon an all zero column appears necessarily at the ROM output bus 33.

The dot columns to the extent they are printed, i.e., to the extent a column contains bits of value 1 to be printed by burning dots into' the tape, should be printed at a constant column spacing thereon. It is, therefore, necessary, to provide very accurately constant timing in the sequence. of presentation of data columns from the sub-array. That presentation depends on (1) a constant rate of column addressing, as provided to the input terminals 34 and (2), on a constant rate of calling the data from the read-out busses 33. in order to provide this constant rate sequence of data presentation, the following arrangement is made.

Beginning with the print command signal as provided at input terminal 31, there is provided a flip-flop which can also be called a print control flip-flop 40 that is being set by the print command signal. Therefore, the flip-flop may respond to the trailing edge of the print command pulse as provided into the line 31 from the external device.

The flip-flop 40, when set, causes solenoid 22 to be energized; there being a suitable power amplifier 24 interposed. Additionally, flip-flop 40, when set, enables an oscillator 41, which is disabled as long as flip-flop 40 is in the reset state. The oscillator includes as principal elements a capacitor 42 and a uni-junction transistor 43, with an output stage 44 and an output amplifier 45 The oscillator 41 provides oscillations at a very accurate rate, for example, at a rate below 1 kilocycle. The oscillations are composed of pulses of short duration, well under a millisecond, each followed by a comparatively long pause of, e.g., 3 milliseconds or thereabouts for a maximum print rate of about 50 characters per second. Oscillation pulses result from rapid discharge of capacitor 42; the pause is defined by recharging the capacitor up to firing level of the transistor. The capacitor 42 is normally discharged and begins to charge only when flip-flop 40 is set. Therefor, oscillations begin at a precise phase relative to the print command pulse and setting of flip-flop 40. The relative slow charge and rapid discharge alternating sequence can recur only as long as flip-flop 40 stays set.

The output pulses, as derived with sufficient amplitude from amplifier 45, are fed to a binary counter 46 having three stages which are connected to the input lines 34 to provide the sub-array column addressing have addressing code 000, this all-zero data column is particularly presented prior to and during the first oscillation period, prior to the first output pulse thereof. During this period, solenoid 22 responds and the tape accelerates. That period is about 3 milliseconds and amply suffices to bring the tape up to rated, constant speed.

The counter 46 begins to count with the first oscillation pulse and that, in turn, causes the second column to be addressed in the ROM chip and the first data column is presented on output bus 33. The counter progresses through the several states, and the data in the sequentially addressed sub-array columns are correspondingly presented at the addressing rate in the output busses 33-1 through 33-7.

The highest count state is sensed by an AND gate 47 responding, in effect, to a setting of all bistable stages that are included in the counter 46. The response of the count-state-7-detector-gate 47 causes the counter to be reset and to stay reset as long as no pulses or additional count pulses are received. This condition is insured in that the count state 7 signal causes flip-flop 40 to be reset, thereby disabling oscillator 41. Also, solenoid 22 is immediately disabled and the tape stops actually within about a millisecond. The reset state of the flipflop does, in effect, force a slow rate discharge of capacitor 42 other than through the output circuits, so that an output pulse is not produced, and a discharge state is established to cause the oscillator 41 to be ready for the next print operation that may occur very soon thereafter;

In essence, the maximum print delay between two character print commands may be about one oscillating period of oscillator 41. That, in turn, establishes the maximum character rate of printing. The constancy of operation of the oscillator 41 insures that the progression of counter 46 is very accurate so that the addressing sequence for the columns of the character code addressed sub-array in ROM chip 32 are run through at very accurate timing. Therefore, the date (bit) columns are, in fact, presented in output bus 33 in accurately determined sequence of timing.

Output transistors 35, altogether seven in number, connect to the output lines 33 of the ROM chip. Particularly, their base electrodes are connected to these output lines, and they serve as gates in that their respective emitters are biased only for a very accurately determined print period within each oscillator period and counter state That print period is derived from a single shot or monostable multivibrator 48 being triggered through an AND gate 49 by each of the oscillator output pulses, as derivable from amplifier 45. The single shot 48 provides pulses of broader width as compared with the width of the pulses provided by oscillator 41. The width of the print pulse may be typically, for example, 1.5 milliseconds. These print pulses determine the duration of print contact finger energization.

Each of these seven data output transistors 35 when enabled, and in response to a data bit l triggers and enables a high voltage transistor switch of a plurality 36, respectively connected to the seven electrodes or contact fingers 20. The output voltage of switches 36 is high in comparison with the usual low voltage as employed in logic circuit, ROM's etc., as described. The voltage that may be switched by the individual switches of circuit 36 maybe 120 volts relative to ground. Such voltage suffices to provide arcing between the respective f inger electrode and the grounded layer in thetape I 1 does not occur. It was found that the resulting printing operation produces characters of vary'accurate spacing. Each dot, and allthe dots in a column are printed by arcing in response to a pulse from SSH 48. These pulses follow each other at oscillator rate and have consjtant'duration. The printing may well be on a stop and go basis, and even then the spacing-between characters remains accurately constant. The printcolumns for each characterjare spaced equidistantly by operation of the synchronous motor as functionally, but not structurally, cooperating with the oscillator 41. It is not necessary to meter incremental progression of the paper so as to insure accurate spacing of print columns. The oscillator operation provides accurately spaced column addressing, and that addressing progression insures a constant rate of data column presentation for purposes of dot printing. I

Finally, it should be noted that the total interval and I path of transportation alsobecomes rather accurately metered. The period frornflip-flop setting to resetting is defined by the duration of eight pulses produced by the oscillator 4i. Asthe oscillator 41 begins at a very accurate zero state, it begins with a full cycle, essentially undistorted, and cycle for cycle is tacked on end to end. As counter 46 reaches count state 7, flip flop 40 is reset preciselyafter seven clock pulses, As aconsequence, the duration of energization of the solenoid is very accurately determined and that, in turn, is sufficient to provide a very'constant rate of progression for the paper in each printing step. When we speak of a very constant accurately rate of progression, this is to mean that variations are not visible in the print result and, of course, a higheraccuracy is not needed.

The invention is not limited to the embodiments described about but all changes and modifications thereof not constituting departures from the spirit and scope of the invention are intended to be included. We claim: 1. A strip printer wherein an electrosensitive strip is reeled past plural, vertically aligned electrodes, comprising in combination: a capstan-pinch roller combination for reeling the strip past the electrodes; a constant speed motor driving the capstan on a continuous basis; I I solenoid means coupled to the pinch roller for selec- T tive, actuation of the pinch roller for engagement of the strip by the pinch roller and the capstan; a read only memory having character input, column addressing input and data outputlines for providing sequentially data groups in the data output 8 lines in response to signals at the-character input and in further response to sequential column addressing input signals; I first circuit means connected to the data lines and connected respectively to the electrodes for control of electric energization thereof inrespo'nse to output signals on the data lines; an addressingcounter connected to thecolumn addressing inputs of the memory, for providing thereto the column addressing signals; I I i constant frequency oscillator means for providing oscillations to the counter ata particularphase in relation to an enablinginputsignal and for the duration of the enabling signal, so that a particular plurality of data columns in the memory are addressed in sequence ,and at a constant rate for causing energization signals to be applied tothe electrodes at said rate; and second circuit means connected for receiving'a print command signal for providing the oscillator enabling signal in response thereto and in timed relation to energization of the solenoid. 2. A strip printer as in claim 1, wherein the pinch roller is journalled in apivotablevcradle,the solenoid having a plunger for pivoting the cradle for the pinch roller to engage the strip in radial alignment with the capstan.

3; A strip printer as in claim 2, wherein the constant speed motor is a synchronous motor.

4. A strip printer as in claim 2, wherein the strip is reeled from a non-driven supply reel, the cradle being freely pivotable, unbiased, except upon engagementby the plunger in response to energization of the solenoid.

5. A strip printer as inclaim 1, wherein the capstan has a knurled periphery and is'maintained at ground potential, to apply ground potential to the strip.

6. A strip printer as in claim, l, the oscillator being normally at rest and started by the second circuit means at a particular phase in response to a print command signal 7. A strip printer as in claim 6, and including additional circuit means connected to the counter for disabling the oscillator and the solenoid in response to a particular count state of the counter.

8. A strip printer as in claim 1, wherein the second circuit means include a flip-flop that is set in response to a print command signal accompanying the providing of character input signals for the memory, said flip-flop being reset in response to a particular count state of the counter, the oscillator being enabled and the solenoid being energized for the duration of the set state of the flip-flop.

9. A strip printer as in claim 1, wherein the strip is run along and in engagement with a grounded platen.

10. A strip printer as in claim 1, wherein ground potential is applied to the strip from both sides.

11. A strip'p rinter as in claim 1, including an additional sensing electrode juxtaposed to said vertically aligned electrodes forsensing the presence of the strip adjacent said vertically aligned electrodes and providing a disabling signal to the first circuit means when the strip is'not in contact with said sensing electrode. 

1. A strip printer wherein an electrosensitive strip is reeled past plural, vertically aligned electrodes, comprising in combination: a capstan-pinch roller combination for reeling the strip past the electrodes; a constant speed motor driving the capstan on a continuous basis; solenoid means coupled to the pinch roller for selective actuation of the pinch roller for engagement of the strip by the pinch roller and the capstan; a read only memory having character input, column addressing input and data output lines for providing sequentially data groups in the data output lines in response to signals at the character input and in further response to sequential column addressing input signals; first circuit means connected to the data lines and connected respectively to the electrodes for control of electric energization thereof in response to output signals on the data lines; an addressing counter connected to the column addressing inputs of the memory for providing thereto the column addressing signals; constant frequency oscillator means for providing oscillations to the counter at a particular phase in relation to an enabling input signal and for the duration of the enabling signal, so that a particular plurality of data columns in the memory are addressed in sequence and at a constant rate for causing energization signals to be applied to the electrodes at said rate; and second circuit means connected for receiving a print command signal for providing the oscillator enabling signal in response thereto and in timed relation to energization of the solenoid.
 2. A strip printer as in claim 1, wherein the pinch roller is journalled in a pivotable cradle, the solenoid having a plunger for pivoting the cradle for the pinch roller to engage the strip in radial alignment with the capstan.
 3. A strip printer as in claim 2, wherein the constant speed motor is a synchronous motor.
 4. A strip printer as in claim 2, wherein the strip is reeled from a non-driven supply reel, the cradle being freely pivotable, unbiased, except upon engagement by the plunger in response to energization of the solenoid.
 5. A strip printer as in claim 1, wherein the capstan has a knurled periphery and is maintained at ground potential, to apply ground potential to the strip.
 6. A strip printer as in claim 1, the oscillator being normally at rest and started by the second circuit means at a particular phase in response to a print command signal.
 7. A strip printer as in claim 6, and including additional circuit means connected to the counter for disabling the oscillator and the solenoid in response to a particular count state of the counter.
 8. A strip printer as in claim 1, wherein the second circuit means include a flip-flop that is set in response to a print command signal accompanying the providing of character input signals for the memory, said flip-flop being reset in response to a particular count state of the counter, the oscillator being enabled and the solenoid being energized for the duration of the set state of the flip-flop.
 9. A strip printer as in claim 1, wherEin the strip is run along and in engagement with a grounded platen.
 10. A strip printer as in claim 1, wherein ground potential is applied to the strip from both sides.
 11. A strip printer as in claim 1, including an additional sensing electrode juxtaposed to said vertically aligned electrodes for sensing the presence of the strip adjacent said vertically aligned electrodes and providing a disabling signal to the first circuit means when the strip is not in contact with said sensing electrode. 